Baghdad, Dec 17 (IANS): A suicide bomber and bombs killed at least 12 people and wounded 39 in Iraq Tuesday, in attacks mostly targeting Shia pilgrims, who will mark the major religious commemoration of Arbaeen next week, a police source said.

In one attack, a suicide bomber blew up his explosive vest among Shia pilgrims near the town of Mahmoudiyah, some 30 km south of Iraq's capital Baghdad, killing four pilgrims and wounding 13 others, the source told Xinhua on condition of anonymity.

Three more Shia pilgrims were killed and seven wounded when gunmen threw two hand grenades at their procession in New Baghdad district in the southeastern part of the capital, the source said.

In addition, two pilgrims were killed and 15 wounded when gunmen threw another hand grenade at a group of Shia pilgrims in Baghdad's eastern district of Mashtal, the source added.

The pilgrims usually travel on foot from different parts of Iraq heading to the holy Shia city of Karbala, some 110 km south of Baghdad, to observe the Arbaeen religious ritual ahead of its climax day next Tuesday.

Arbaeen is the 40th day after the martyrdom anniversary of Imam Hussein, Prophet Muhammad's grandson and the third holy figure for the Shia Muslim sect, who was killed in the battle of Karbala in 680 A.D.

Separately, gunmen attacked a police checkpoint near the city of Baiji, some 200 km north of Baghdad, killing two policemen and wounding another, a local police source told Xinhua.

Also in Baiji, a police officer was killed around noon when a sticky bomb attached to his car exploded while he was driving in the central part of the city, the source said.

Meanwhile, a roadside bomb struck a police patrol in the city of Samarra, some 120 km north of Baghdad, destroying a police vehicle and wounding three policemen, the source added.

Many Iraqis are worried about a resurgence of violence and ethnic and sectarian strife that nearly tore the country apart a few years ago.